This description relates to a method and apparatus for the treatment of water. In particular, the method and apparatus may be used to treat aqueous solutions to make those aqueous solutions more desirable or fit for disposal, either back to the environment or to render such aqueous solutions more fit for further treatment in other treatment facilities.
In the field of water treatment, great efforts have been made to deal with disinfection of water. Aqueous solutions requiring treatment include fluids some times referred to as grey water, that is, water which may be produced domestically, containing soap, washing fluids, and the like. Treatment is also required of black water, which is commonly referred to as sewage. There is no real difference between the biological and chemical profiles of grey water and black water. There is no real separation between grey water and black water and in most household situations, all such water is treated as though it were sewage. Sewage is often treated by central, municipally operated treatment plants. However, sewage is often also treated in local facilities, some times referred to as septic tanks. There are a number of options for local treatment competitive with septic tank treatment technology including various forms of bio-digesters and the like.
There are many other fluids which are not suitable for general disposal back to the atmosphere. Some examples in addition to grey/black water, domestic or industrial sewage include septage, leachate, pharmaceutical waste streams and ship ballast fluids.
Onsite wastewater treatment systems (OWTS) include systems that serve small communities, resorts, industry, and individual private residences not serviced by municipal infrastructure. It is this last group, individual private residences, or isolated resorts, with which we are particularly concerned because existing technologies have limited performance and a complete lack of supervision. The vast majority of these systems are septic systems, or involve disposal of untreated waste streams. Septic systems appeared over 100 years ago on farm properties with large tracts of virgin earth. These systems include a septic tank (collector/concentrator), some form of leaching bed (receiver), and the surrounding soil (distributor). This is primitive technology including anaerobic digestion followed by aeration and natural adsorption by the earth. These systems provide little disinfection (pathogens) and limited denutrification (carbon, phosphorus, and nitrogen). (Leverenz et al., 2002)(1). Regulations for these systems have not changed appreciably in over 40 years. The Ontario Rural Wastewater Centre at the University of Guelph states, “There are over 1 million septic systems in Ontario alone . . . High levels of rural groundwater contamination indicates that many of these systems are working below acceptable levels and changes are required to alleviate the problem.” “Water quality problems in the rural portions of Canada are large and occur throughout the country.” (Joy et al., 2001)(2).
In the case of septic tanks or similar systems, a processing tank (reactor) is normally provided. In order to keep the septic tank system working for its normal useful life, the septic tank is intended to be pumped periodically to remove the solids and heavy liquids which collect in the bottom of the septic tank. This pumped out material is often referred to as septage. In some jurisdictions, septage can be distributed over agricultural land provided that the septage is widely distributed so as to have an acceptable local effect so that natural digestion of the material is safely accomplished. However, a number of jurisdictions are either banning outright or severely restricting the amount of septage that can be spread on the ground. Where such regulations exist, then septage must be treated in a municipal operated sewage treatment system or some such similar facility. Septage is, in large measure, a concentrated collection of materials precipitated in the septic tank and may require significant dilution before being acceptable to the operator of the treatment facility.
Increasingly, this primitive technology has been used on much smaller tracts of land and waterfront properties. The result has been increased contamination of wells with pathogens and overload of water bodies with nutrients. Once these contaminants are in groundwater, they eventually reach rivers and lakes. In other words, once there is a pollution problem, it may be only a step away from a water supply problem. (Environment Canada—Groundwater Contamination)(3). The need for new technology was clear. In response to this need, enhancements were designed to operate in conjunction with traditional systems. These included both media bioreactors and membrane bioreactors. Those add-ons provided improved disinfection, good reduction of suspended solids and carbonaceous compounds and fair reduction of nitrogen, with re-circulation, but little reduction of phosphorus. While these systems were tested on sewage and provided acceptable results, they were expected to process septage, and the results were not very good.
Rain or ground water passing through a waste dump site, can leach various compounds from the dump. The water collected at the bottom of a dump site is some times referred to as leachate. Leachate can be a significant source of what is termed “pollution”, that is, material being released to the environment which is not acceptable in the environment. It would be desirable to have a system for treating leachate, which is an aqueous solution, to make the leachate more suitable for either release to the environment or for further treatment in other treatment facilities.
It is becoming recognized, that treated water flowing from some treatment plants is a source which releases pharmaceuticals into the environment. When mammals are prescribed pharmaceuticals, the pharmaceuticals are introduced into the body and utilized by the body. However, in most cases, the pharmaceutical is not completely metabolized in the body. Thus, at least some of the pharmaceuticals injested may be excreted from the body. Also, many pharmaceuticals are designed to be stable (non-reactive) in a bacterial environment (namely the human gut) and are not broken down in bioreactors. In other cases, some of the medicine may be metabolized to secondary compounds, but not utilized by the body, and these also are excreted, and then become a component in sewage. Often these pharmaceuticals, whether as primary products or as secondary products, are not effectively treated in some sewage treatment plants. This results in pharmaceuticals being released into the environment.
Cargo ships and other large vessels often take on or discharge ballast water to control ship operating parameters. Discharge of untreated ballast water may involve release of invasive pathogens and species into non-native environments. Thus, there is a need to treat ballast water prior to release to inhibit these problems.
Thus, there are many sources of aqueous solutions that could benefit by treatment. In some cases the treatment may be satisfactory to give treated aqueous solution acceptable for disposal, while in other cases the treatment may render the aqueous solution a more acceptable product for further treatment in other facilities.
The emerging concern over compounds including disinfection by-products (DBPs), volatile organic compounds (VOCs), and pharmaceuticals (PHARMA) in both drinking water and the environment, has created a whole new dimension for the needed capabilities of private residential OWTS. Existing technology, both traditional and enhanced, have little chance of effectively reducing these compounds in a timely way. Without new technology, collectively the uncontrolled discharge from these private residential OWTS, will become the largest contributor of compounds of emerging concern (CECs) to the environment.
U.S. Pat. Nos. 6,402,945 and 6,673,251 illustrate an apparatus and system for treating aqueous solutions by injecting ozone into a recirculation conduit. While those patents illustrate useful methods and apparatus, it would be advantageous to have a process and system which not only disinfects, but also has other beneficial affects on the treatment of the aqueous solution.
Among other of the components of sewage are typically phosphorus and nitrogen. Where there are a concentration of septic systems such as in rural homes or cottages surrounding a lake or river, there may eventually be an overload of phosphorus and nitrogen compounds released by the septic systems into the ground water and ultimately, the lake or river. As development around a localized water resource occurs, there will ultimately become a point at which the natural environment will not be able to safely handle the amount of phosphorus and nitrogen released from the septic systems. When the presence of these nutrients increases, certain plant species such as algae or phytoplankton can grow above normal levels which in turn causes problems for the other species trying to grow around them. Excessive algae growth blocks sunlight from the vegetation beneath the water's surface which can cause massive die off of plant species. It also produces a significant amount of organic material that also uses up valuable oxygen as it decomposes and contributes to foul smelling and tasting water.